The invention is based on a cooling fan according to the preamble to claim 1.
Internal combustion engines are frequently cooled to a desired operating temperature by electrically driven cooling fans. Known cooling fans having two-speed electric motors or electric motors with series resistors must be frequently switched on and off in order to maintain a precise operating temperature. They are intermittently operated with an unnecessarily high speed and then are switched off again at a particular temperature, as a result of which more energy than necessary is expended for the cooling process and the temperature of the internal combustion engine fluctuates around the optimal temperature, usually slightly above or below it. Both lead to an increased energy demand and therefore to an increased fuel consumption. Furthermore, unnecessarily high fan noise is produced.
In order to prevent this, a cooling fan in modern motor vehicles is regulated by a control unit which smoothly adjusts the speed of a cooling fan to corresponding operating states. The control unit is an additional component which is affixed in the engine compartment separate from the cooling fan, preferably in a cool region, so that the electronics are not damaged or destroyed by high temperatures, for example in the vicinity of a headlight. The mounting location of the control unit can vary and can be different distances from the cooling fan, depending on the layout of the engine compartment in different motor vehicles, construction machines, and other machines driven by internal combustion engines. As the distance increases, so do the materials expenditures for cable and fasteners and the installation expense. Furthermore, longer cable routings lead to electromagnetic interference, for example interference with the internal combustion engine control or interference with a radio.
The cooling fan according to the invention has a support structure, also referred to as a frame or housing, into which a control unit is integrated, i.e. it is fastened onto or into the frame. The cooling fan is a functional component that can be suitably developed as a whole in one place and can be optimized with regard to its function, noise production, and effectiveness. Furthermore, the cooling fan can be suitably preassembled and then its function can be fully tested before installation into a motor vehicle. Possible damage to the control unit in a separate assembly is prevented and additional space in the engine compartment is no longer required.
In all uses of the cooling fan, the control unit is fastened into or onto the frame and is protected against external influences. Because of its spatial connection to the cooling fan, the control unit is easy to find and access when testing the function of the cooling fan in a workshop, regardless of the vehicle type. All of the cables can be advantageously united in the frame to form an interface or plug connector, by means of which the cooling fan can be connected in a particularly simple and rapid fashion. Generally, plug connectors are cost intensive components and are frequently the weak point in the system. Having only one plug connector or one interface reduces the number of weak points and components, and reduces costs.
The distance from the control unit to the electric motor of the cooling fan is particularly short, as a result of which a short reaction time of the cooling fan can be achieved and in a small and limited span, no disturbance variables or only slight disturbance variables such as electromagnetic waves can travel outward from the control unit and/or the electric motor and possibly act externally on the control unit. Due to the small distance, there are savings in cable length and fasteners such as clamps, etc. Fewer components have to be mounted in the final assembly. The assembly as a whole is simplified and the cost is reduced.
In one embodiment of the invention, the proposal is made to affix the control unit to the baffle apparatus in the air flow of a fan propeller and thereby usually also in the relative wind of the motor vehicle. The control unit is directly exposed to the air flow, is cooled particularly well by a high convection, and is thereby protected from overheating even at high temperatures in the engine compartment. It is therefore possible and usually for space reasons also advantageous to fasten the control unit on the side of the baffle apparatus oriented toward the internal combustion engine. Additional cooling devices or insulation devices for the control unit are no longer necessary. Preferably, the control unit replaces and/or supports one or more struts of the frame, as a result of which this frame can be dimensioned as weaker and there can thus be weight and space savings. Moreover, the cooling module to which the regulator is affixed is insulated against oscillation. It is not necessary for there to be a separate decoupling from the vehicle body, e.g. by means of a rubber damper.
Primarily the temperature of the internal combustion engine is used as a regulating variable for the control unit and is usually detected by means of the coolant temperature, wherein additional variables of the operating state, e.g. the motor vehicle being at rest, speed of the engine, etc., can also be used by the control unit in order to react to temperature changes as early as possible. Furthermore, the control unit can be used for the detection of defects such as a defective electric motor, a jammed fan propeller, etc., and also to perform safety functions. According to the invention, the control unit performs the safety function of limiting the output of the electric motor. The cooling fan is thus an intrinsically automatic and safeguarded system, by means of which additional safety devices besides the cooling fan are no longer necessary. The cooling fan absorbs switching peaks which can damage the electric motor, allows the electric motor to accelerate smoothly, and limits the maximal current.